This particular climber, like wisteria, should have been pruned back to 2 buds on the stems (laterals) by mid February (late winter). It is somewhat late to do it now, unless your weather has remained very cold for the last few weeks. Prune only what you need to this year, and remember to do it at the right time (before the end of February, while its dormant) next year.

Worse comes to worst, you can chop it down to the ground, and it will come back from the roots, though it may be nearly fall before it blooms!